This application relates generally to voice coil motors and more particularly to a coil construction for a voice coil motor.
In a disc drive, a head for reading and writing data to and from a disc is supported on an actuator arm. The actuator arm controls the position of the head through the use of a voice coil motor (VCM), which typically includes a coil attached to an actuator assembly, as well as one or more permanent magnets which establish a magnetic field in which the coil is immersed. The controlled application of current to the coil causes magnetic interaction between the permanent magnets and the coil so that the coil moves in accordance with the well-known Lorentz relationship. As the coil moves, the actuator assembly pivots about a bearing shaft assembly, and the head (or heads) is caused to move across the surfaces of the discs.
The coil is fabricated by winding copper wire around a mandrel. Adhesion of a coil wire to the adjacent wires is accomplished by pre-coating the wire with a bond coat material and then heating the covered wire while winding the coil. The coil is heated to allow plasticizers to outgas from the coating. During this process, voids can form in the bond coat, which can result in delaminating of the bond coat from the wires. The delamination can allow individual wires in the coil to vibrate, causing undesirable noise during operation. A wire may also contact an adjacent wire if it becomes unbonded further causing undesired vibration effects. Another source of noise or unwanted vibration in current coils is out-of-plane forces. These forces cause additional vibration of the voice coil motor.
Accordingly there is a need for a coil construction that reduces the undesirable vibration due to delamination and out-of-plane forces. The present invention provides a solution to this and other problems, and offers other advantages over the prior art.
Against this backdrop the present invention has been developed. One embodiment of the present invention is directed to a coil construction for a voice coil motor. The coil construction includes a series of planar coils made from electrically conductive material formed on a substrate. The planar coils are disposed on a substrate and the coils are formed into a stacked array wherein each planar coil is separated from its neighboring coil or coils by a dampening material. The coil construction is assembled into an actuator arm for use in a disc drive and used to position a head located on the actuator arm.
Another embodiment of the invention is directed to a disc drive assembly including an actuator arm assembly for positioning a head over a disc surface. A coil construction is disposed on the actuator arm assembly and current from control circuitry through the coil construction controls the position of the head over the disc surface. The coil is a part of a voice coil motor that creates forces to move the actuator arm assembly to position the head. The coil construction includes a series of adjacent layers of stacked planar coils disposed on a substrate. The planar coils are electrically connected in series to form a single electrical current path.
These and various other features as well as advantages which characterize the present invention will be apparent from a reading of the following detailed description and a review of the associated drawings.